(display "\n========================================\n")
(define (square-list items)
    (if (null? items)
        ()
        (cons (square (car items))
              (square-list (cdr items)))))

(display (square-list (list 1 2 3 4)))
(newline)

(define (map proc items)
    (if (null? items)
        ()
        (cons (proc (car items))
              (map proc (cdr items)))))

(define (square-list items)
    (map (lambda (x) (* x x)) items))
(display (square-list (list 1 2 3 4)))

(display "\n========================================\n")
